This is the js file. it isn't that bad.

jquery-fileFypeIcon.js

(function($) {
  this.FileLink = function(filename){
    this.filename = filename;
  };

  FileLink.prototype = {
    LAST_URL_SECTION_PATTERN: /\/?([^\/]+)$/i,
    BEFORE_QUERY_STRING_PATTERN: /^([^?]+)/i,
    FILE_EXTENSION_PATTERN: /\.([^\.]*)$/i,
    extension: function(){
      var lastUrlSection = this.filename.match(this.LAST_URL_SECTION_PATTERN)[1];
      var bareFilename = lastUrlSection.match(this.BEFORE_QUERY_STRING_PATTERN)[1];
      return bareFilename.match(this.FILE_EXTENSION_PATTERN)[1];
    }
  };

  $.fn.addFileTypeIcon = function(){
    return this.each(function(){
      $('a', $(this)).each(function(){
        var fileLink = new FileLink($(this).attr('href'));
        $(this).addClass(fileLink.extension());
        $(this).addClass('file-text');
        $(this).prepend($('<span>').addClass('file-icon'));
      });
    });
  };
})(jQuery);